Building a "favorite this" system and totally stuck

[eluser]gullah[/eluser]
I have a similar system going and I did something like this.

User Table
id

votes table
id
user_id
item_id

Item table
id
vote_up
vote_down

when someone goes to the page/or submits their vote you can check the votes table to see if they have already voted pretty easily by using the session information you have setup, and the item id from the url or wherever. Hope this helps.